Recently, as next-generation solid-state nonvolatile memories capable of high-speed reading/writing, high capacity, and low-power-operation, magnetic random access memories (MRAM) that use the magnetoresistive effect of a ferromagnetic body have been drawing increasing attention. In particular, a spin-transfer torque writing type MRAM that uses, as a storage layer, a perpendicular magnetization film having a magnetization easy axis in a direction perpendicular to a film plane is advantageous to write current reduction and higher capacity. A magnetoresistive element having a ferromagnetic tunnel junction used in this MRAM has been attracting attention since the discovery of a high magnetoresistance ratio shown by this magnetoresistive element. The magnetoresistive element comprises a storage layer variable in magnetization direction, a reference layer that maintains a predetermined magnetization direction, and a nonmagnetic layer disposed between the storage layer and the reference layer.
A material which constitutes the conventional storage layer and which has perpendicular magnetic anisotropy is an alloy or stack of a magnetic material, Co, Fe and Ni which are magnetic materials, Pt, Pd or the like, and Tb, Dy or the like. However, Pt, Pd, Tb, Dy and the like increase the friction factor of the magnetic material, and, in a heat treatment process, diffuse in the vicinity of MgO and change its electric characteristics, and further decrease the degree of magnetic anisotropy. Thus, there have heretofore been no available materials that allow for both current reduction by the decrease of the friction factor and the process heat resistance of electric and magnetic characteristics. For example, a CoPd alloy is high in perpendicular magnetic anisotropy, but has a disadvantage of being also high in friction factor and being nonresistant to a process heat (thermal disturbance) of about 350° C.